In sterilizing foods, particularly goods being heated, cooked, or sterilized on a mass-production basis, it is necessary to ascertain that the heater is functioning at the desired level, to bring the food within the container to the desired temperature.
In accordance with the present invention, it has been determined that it is desirable not only to ascertain that the desired temperature level is reached, but to ascertain if the desired temperature level is reached for all of the product within the container, especially at the center of the can or other container. Even further, it is deemed to be desirable to ascertain the length of time that the food product at the center of the container (generally the last portion of food product to reach the desired temperature) has remained at the desired temperature.
In so doing, it has been determined that it would be desirable to have an indicating device that would accomplish these ends, and that could be run through that portion of the assembly line process directed to heat treating, as a test container, being exposed to the same heat treatment as are products actually being produced. To this end, a test container is utilized adapted for maintaining the desired device at the center of the container, and preferably immersed in the food product being heated. After the heating operation, the test container may be removed from the assembly line, checked to ascertain if the desired temperature was reached, and the length of time that the desired temperature at the location (preferably center) of the container was maintained at the temperature, in order to ascertain if the heating, cooking, sterilizing, etc. process is functioning as planned.
In order to accomplish these ends, particular time temperature level indicating device has been developed.